Merge pull request #3 from styled-components/ci

add travis yml

Author: quantizor

.travis.yml

@@ -0,0 +1,21 @@
+language: node_js
+dist: trusty
+branches:
+  only:
+    - master
+cache:
+  yarn: true
+  directories:
+    - node_modules
+node_js:
+  - '8'
+jobs:
+  include:
+    - stage: test
+      script:
+        - node --version
+        - yarn --version
+        - yarn test
+notifications:
+  email:
+    on_failure: change